WASHINGTON — A key Senate committee voted on Wednesday to require the Pentagon to strip military bases and equipment of Confederate names, monuments or symbols within three years, setting up an election-year clash with President Trump on the issue amid a rapidly building national outcry against historical representations of racism.
The move by the Armed Services Committee to insert the mandate into a must-pass defense authorization bill, which was supported by Republicans and Democrats alike, came as Mr. Trump publicly declared his refusal to even consider removing any of the names. He raged about it on Twitter on Thursday, exhorting members of his party to resist the effort even as a growing number of Republicans on Capitol Hill said they were open to removing symbols of the Confederacy.
The conflict underscored how isolated the president is becoming, even from members of his own party, as protests of police brutality against black people fuel a broader discussion of race and identity in America.
The break is more than rhetorical. The move to include the proposal, written by Senator Elizabeth Warren, Democrat of Massachusetts, raised the prospect of an election-year Senate vote on the issue.
“The American people know these names have to go,” Speaker Nancy Pelosi said at a news conference on Thursday. The president, she continued, “seems to be the only person left who doesn’t get it.”
Republican lawmakers’ willingness to break with the president on the issue comes as they have also distanced themselves from his bellicose response to the protests, instead scrambling to come up with a plan to combat racism in policing.
Dramatizing the rift between Mr. Trump and members of his own party, he lashed out on Twitter on Thursday afternoon, apparently dismayed by the support the measure was picking up in Congress.
“Seriously failed presidential candidate, Senator Elizabeth ‘Pocahontas’ Warren, just introduced an Amendment on the renaming of many of our legendary Military Bases from which we trained to WIN two World Wars,” Mr. Trump tweeted. “Hopefully our great Republican Senators won’t fall for this!”
But the president’s message came as many Republicans on Capitol Hill had already endorsed or expressed openness to the idea, including the top leader in the House and several Republican senators. He posted it the day after the closed-door vote on the proposal, which would require the Defense Department to set up a panel to develop a plan to rename, within the next three years, military bases and other assets currently named for Confederate figures. The vote happened after Mr. Trump announced that his administration would not consider the idea.
The proposal includes a measure that would exempt “grave markers” from the ban on Confederate symbols and markers, Senate aides familiar with the details said.
The panel also included a measure that would ban the use of military force against peaceful protesters, a direct response to Mr. Trump’s threat to call in the armed forces to quell unrest throughout the country, and the use of the National Guard to confront protesters in Washington, D.C.
On Thursday, Representative Kevin McCarthy, Republican of California and the minority leader, told reporters he was “not opposed” to renaming the bases named for Confederate figures.
“There are a number of people in the armed services who think it could be appropriate to change some,” he said, citing Defense Secretary Mark T. Esper, who has said he is open to renaming bases. “Some would say otherwise not to.”
Senator Roy Blunt, Republican of Missouri, said he “didn’t have any problem” with the idea “at all,” and added that “there’s been lots of great soldiers since the Civil War” whose names could go on forts.
“Braxton Bragg was probably the worst commanding general in the Confederate Army,” he continued, singling out Fort Bragg in North Carolina. “Interesting general to name a fort after.”
Senator James Lankford, Republican of Oklahoma, held back from supporting renaming the bases, but said it was important to start a discussion about why they were named after Confederates in the first place.
“A lot of those statues and monuments were put there to kind of declare, ‘We’re not going to integrate,’” Mr. Lankford said. “I think we should acknowledge that and, say, ‘No, we are.’ And for those that were digging in during the time of Jim Crow, they need to know that time has passed.”
By Thursday afternoon, only a handful of Republicans spoke out against the proposal. Senator James M. Inhofe of Oklahoma, the chairman of the Armed Services Committee, said he felt the issue “should be decided by the local communities and states, as opposed to mandating something that maybe the people don’t want.”
Senator Josh Hawley of Missouri, who sits on the panel, told reporters he had risen in opposition to the bill shortly before the vote.
“I don’t think Congress mandating these being renamed and attempting to erase that part of our history is the way you deal with that history,” Mr. Hawley said.
The push in the Senate came on the same day that Ms. Pelosi reiterated a longstanding call for the removal of 11 statues of Confederate soldiers — including Jefferson Davis and Alexander Stephens, the president and vice president of the Confederate States of America — that are displayed in the Capitol.
“They committed treason, and their statues are in the Capitol,” Ms. Pelosi said. “These names have to come from these bases and the statues have to go from the Capitol.”
Those statues were selected and donated by states to the Capitol, and current federal law places the power to remove a statue with the states.
Senator Mitch McConnell, Republican of Kentucky and the majority leader, said on Thursday that allowing the states to decide whether to replace the statues was “the appropriate way” to deal with the issue.
Mr. Blunt, the chairman of the panel in charge of handling such a request, said on Thursday that seven states had already moved to replace their statues, four of which had been singled out by Ms. Pelosi.
“There is clearly an agreement that the federal government has made mistakes,” he said. “I’m glad to see the states replacing some of these statues with statues of people that are more reflective of either the entire history of the country, or even the recent history of the country.”
Luke Broadwater and Emily Cochrane contributed reporting.